Java中多態的實例

public class cf {

    /**
     * 實際上這里涉及方法調用的優先問題，
     * 優先級由高到低依次為：this.show(O)、super.show(O)、this.show((super)O)、super.show((super)O)。
     */
    public static void main(String[] args) {

        A a1 = new A();
        A a2 = new B();
        B b = new B();
        C c = new C();
        D d = new D();
        System.out.println(a1.show(b)); // ① A and A
        System.out.println(a1.show(c)); // ② A and A
        System.out.println(a1.show(d)); // ③ A and D
        System.out.println(a2.show(b)); // ④ B and A
        System.out.println(a2.show(c)); // ⑤ B and A
        System.out.println(a2.show(d)); // ⑥ A and D
        System.out.println(b.show(b)); // ⑦ B and B
        System.out.println(b.show(c)); // ⑧ B and B
        System.out.println(b.show(d)); // A and D
    }
}

class A {
    public String show(D obj) {
        return ("A and D");
    }

    public String show(A obj) {
        return ("A and A");
    }
}

class B extends A {
    public String show(B obj) {
        return ("B and B");
    }

    public String show(A obj) {
        return ("B and A");
    }
}

class C extends B {
}

class D extends B {
}

 

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